AD 72-08-04
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Hartzell Propeller, Inc. | HC-B3T | HARTZELL Models HC-B3TN-2, HC-B3TN-3, HC-B3TN-5, HC-B3TF-7, and HC-B4TN-3 Series Propellers |
| aircraft | Hartzell Propeller, Inc. | HC-B4TN-3 | HARTZELL Models HC-B3TN-2, HC-B3TN-3, HC-B3TN-5, HC-B3TF-7, and HC-B4TN-3 Series Propellers |
Unsafe Condition
Propeller blade failures due to cracks in the interior surfaces of the balance hole, which may originate from lead wool installation or insufficient shot peening.
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Required Actions
Inspect blades for cracks in the balance hole area using dye penetrant or approved method. Shot peen balance holes and service per Hartzell Bulletin No. 97. Replace cracked blades before flight. For Beech 99/A99 aircraft, retire blades after 1500 hours post-inspection/shot peening by replacing with T10173-Category II blades.
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Compliance Time
Compliance required as indicated in the directive: inspections within 100 or 15 hours' time in service after effective date, depending on total hours. Propellers with unknown time assume 1400 hours. Blade replacement for Beech 99/A99 must occur within 1500 hours after inspection/shot peening.
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Affected Aircraft
Hartzell HC-B3TN-2, HC-B3TN-3, HC-B3TN-5, HC-B3TF-7, and HC-B4TN-3 series propellers with T10173 or T10176 type blades, excluding specific serial numbers listed in the directive.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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